[pve-devel] [PATCH http-server] fix #4859: properly configure TLSv1.3 only mode

[Fabian Grünbichler]

set_min/max_proto_version is recommended upstream nowadays, and it seems to be
required for some reason if *only* TLS v1.3 is supposed to be enabled.

querying via get_options gives us the union of
- system-wide openssl defaults
- our internal SSL defaults
- flags configured by the user via /etc/default/pveproxy

note that by default only 1.2 and 1.3 are enabled in the first place, so
disabling either leaves a single version being set as both min and max.

Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
---
/etc/default/pveproxy settings and their effect tested with sslscan

 src/PVE/APIServer/AnyEvent.pm | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/PVE/APIServer/AnyEvent.pm b/src/PVE/APIServer/AnyEvent.pm
index 1fd7a74..e5a852b 100644
--- a/src/PVE/APIServer/AnyEvent.pm
+++ b/src/PVE/APIServer/AnyEvent.pm
@@ -2012,6 +2012,23 @@ sub new {
 	    warn "Failed to set TLS 1.3 ciphersuites '$ciphersuites'\n"
 		if !Net::SSLeay::CTX_set_ciphersuites($self->{tls_ctx}->{ctx}, $ciphersuites);
 	}
+
+	my $opts = Net::SSLeay::CTX_get_options($self->{tls_ctx}->{ctx});
+	my $min_version = Net::SSLeay::TLS1_1_VERSION();
+	my $max_version = Net::SSLeay::TLS1_3_VERSION();
+	if ($opts & Net::SSLeay::OP_NO_TLSv1_1) {
+	    $min_version = Net::SSLeay::TLS1_2_VERSION();
+	}
+	if ($opts & Net::SSLeay::OP_NO_TLSv1_2) {
+	    $min_version = Net::SSLeay::TLS1_3_VERSION();
+	}
+	if ($opts & Net::SSLeay::OP_NO_TLSv1_3) {
+	    die "misconfigured TLS settings - cannot disable all supported TLS versions!\n"
+		if $min_version == Net::SSLeay::TLS1_3_VERSION();
+	    $max_version = Net::SSLeay::TLS1_2_VERSION();
+	}
+	Net::SSLeay::CTX_set_min_proto_version($self->{tls_ctx}->{ctx}, $min_version);
+	Net::SSLeay::CTX_set_max_proto_version($self->{tls_ctx}->{ctx}, $max_version);
     }
 
     if ($self->{spiceproxy}) {
-- 
2.39.2